JP2002115087A - Regenerating method for cleaning solution of metallic product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively obtain a cleaning solution without largely consuming energy and without using a reaction furnace causing an environmental problem by effectively utilizing an waste solution to be disposed. SOLUTION: Nitric acid is added in the ratio of 10 to 200 ml based on a waste solution 11 of hydrofluoric acid in which the concentration of fluorine ions is >=3% to obtain a regenerated cleaning solution of which pH is controlled to 1.2 to 5.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a metal product such as a stainless steel pipe by regenerating a hydrofluoric acid waste liquid discharged in a manufacturing process of various industrial products as a cleaning solution for the metal product.

[0002]

2. Description of the Related Art An oxide film is formed on the surface of a metal product by heat treatment in a manufacturing process or by contact with oxygen in the air.
This oxide film is washed and removed to reduce the quality of the product. For example, taking a stainless steel pipe as an example, a plurality of stainless steel pipes having an oxide film formed on the surface are collectively suspended by a wire, and immersed for several minutes in a water tank in which diluted hydrofluoric acid is stored. The oxide film is washed and removed with a stainless steel pipe with a glossy surface.

[0003] Dilute hydrofluoric acid used for washing such a stainless steel pipe is generally manufactured through a manufacturing process shown in a flowchart of FIG. In other words, first, fluorite
In a sulfuric acid stirring step S11, fluorite and sulfuric acid are mixed and stirred, and then, in a reaction furnace charging step S12, the mixture is charged into a reaction furnace such as a rotary kiln and chemically reacted under a temperature condition of 600 ° C. or higher to obtain hydrogen fluoride. Acid, and then the absorption purification step S
The diluted hydrofluoric acid is obtained by adding a large amount of pure water to hydrofluoric acid and diluting it to a fluorine ion concentration of about 3% in a concentration adjusting step S14 after passing through No. 13.

[0004]

However, the use of dilute hydrofluoric acid as the cleaning liquid produced as described above increases as the size of the metal product used for cleaning increases, and the amount of dilute hydrofluoric acid increases. Since the amount of water used is even more enormous, the cost of dilute hydrofluoric acid occupies a large weight in the metal product cleaning process, and some solution has been desired.

[0005] In the above-mentioned diluted hydrofluoric acid production process, there is a problem that a large amount of energy is consumed due to the reaction furnace charging step S12 in order to obtain a new solution of hydrofluoric acid. There are certain fluorite and sulfuric acid and pure water resource consumption problems. In addition, since fluorite and sulfuric acid are chemically reacted under a temperature condition of 600 ° C. or more, there is a problem that smoke is generated and the environment is deteriorated.

[0006] The present invention has been made in view of such a point, and an object of the present invention is to use a waste liquid that is originally disposed of effectively, thereby consuming a large amount of energy and deteriorating the environment. It is to obtain a cleaning solution at a low cost without using a reaction furnace which causes the above.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method of mixing and adjusting waste liquid discharged in various industrial product manufacturing processes such as a semiconductor manufacturing process and reusing it as a cleaning solution for metal products. Specifically, the following solution was taken.

That is, according to the first aspect of the invention, nitric acid is added at a ratio of 10 to 200 ml to 1 liter of a hydrofluoric acid waste liquid having a fluorine ion concentration of 3% or more, so that a pH value of 1.2 to 5. It is characterized in that a regenerated cleaning liquid adjusted to 0 is obtained.

With the above structure, in the first aspect of the invention, the hydrofluoric acid waste liquid having a fluorine ion concentration of 3% or more is revived as a regenerating cleaning liquid.

[0010] Since the regenerated cleaning liquid is obtained from a waste liquid which is originally subjected to disposal, it does not require fluorite or sulfuric acid for producing the cleaning liquid, and a large amount of water is generated by using a reaction furnace in the cleaning liquid generation step. There is no problem of energy consumption, and the cleaning solution can be obtained at low cost. Further, there is no problem of environmental deterioration due to the generation of soot by using the reaction furnace.

Furthermore, the relationship between the amount of the nitric acid waste liquid and the pH changes linearly with the mixing ratio of the hydrofluoric acid waste liquid and the nitric acid as described above, so that the pH adjustment according to the material of the metal product is facilitated. The washing time and washing ability can be freely controlled according to demand.

According to a second aspect of the present invention, in the first aspect of the invention, before adding nitric acid, impurities are removed from a hydrofluoric acid waste liquid having a fluorine ion concentration of 3% or more.

With the above arrangement, in the second aspect of the invention, the hydrofluoric acid waste liquid containing impurities and having a fluorine ion concentration of 3% or more is revived as the regenerating cleaning liquid.

According to a third aspect of the present invention, in the second aspect, before removing impurities from the hydrofluoric acid waste liquid having a fluorine ion concentration of 3% or more, the hydrofluoric acid waste liquid has a fluorine ion concentration of 3%. %, And the diluted hydrofluoric acid waste liquid after removing impurities from the diluted hydrofluoric acid waste liquid is concentrated to obtain a hydrofluoric acid waste liquid having a fluorine ion concentration of 3% or more.

According to the above construction, in the third aspect of the present invention, the hydrofluoric acid waste liquid containing impurities and having a fluorine ion concentration of 3% or more is once diluted and the impurities are removed from the diluted hydrofluoric acid waste liquid. Therefore, the regenerating cleaning solution is quickly revived.

According to a fourth aspect of the present invention, a hydrofluoric acid waste liquid having a fluorine ion concentration of less than 3% is concentrated into a hydrofluoric acid waste liquid having a fluorine ion concentration of 3% or more. 10-200 m of nitric acid per 1 liter of acid waste liquid
By adding at a rate of 1 l, the pH value becomes 1.2-5.
It is characterized in that a regenerated cleaning liquid adjusted to 0 is obtained.

With the above arrangement, in the invention according to the fourth aspect, the hydrofluoric acid waste liquid having a fluorine ion concentration of less than 3% is revived as a regeneration cleaning liquid.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, before concentrating the hydrofluoric acid waste liquid having a fluorine ion concentration of less than 3%, impurities are removed from the hydrofluoric acid waste liquid. And

With the above configuration, in the invention according to the fifth aspect, the hydrofluoric acid waste liquid containing impurities and having a fluorine ion concentration of less than 3% is revived as the regeneration cleaning liquid.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for producing a reclaimed cleaning liquid for a metal product according to an embodiment of the present invention will be described with reference to a stainless steel pipe as an example, but the present invention is not limited to these and can be applied to other metal products. It is.

As described in connection with the conventional example, the stainless steel pipe is immersed in a water tank in which a cleaning liquid is stored because an oxide film is formed on the surface when the stainless steel pipe comes into contact with oxygen in the air in the manufacturing process. The oxide film is washed away to restore the luster.

The greatest feature of the present invention is that a waste liquid discharged in a manufacturing process of various industrial products is used as a cleaning liquid for cleaning and removing the oxide film.
Specific examples include, for example, a diluted hydrofluoric acid waste liquid that is diluted with pure water and discharged in a silicon wafer cleaning step in a semiconductor manufacturing process.

In the liquid crystal panel manufacturing process, it is hydrofluoric acid waste liquid discharged in the cleaning and etching processes of the liquid crystal panel.

In a solar cell product manufacturing process, it is a hydrofluoric acid waste liquid discharged in a solar cell cleaning and etching process.

In a glass product manufacturing process, it is a hydrofluoric acid waste liquid discharged in a glass cleaning and etching process.

In the bulb product manufacturing process, it is hydrofluoric acid waste liquid discharged in the inner surface matting process and the washing process.

In the television product manufacturing process, it is a hydrofluoric acid waste liquid discharged in a cathode ray tube inner surface cleaning process.

In a stone product manufacturing process, it is a hydrofluoric acid waste liquid discharged in a stone surface cleaning process.

In the printed circuit board product manufacturing process, it is hydrofluoric acid waste liquid discharged in the printed circuit board surface cleaning and degreasing processes.

In the automobile manufacturing process, it is hydrofluoric acid waste liquid discharged in the degreasing step of the painting process of the automobile body.

(Embodiment 1) FIG. 1 is a flowchart showing a manufacturing process of a method for manufacturing a regenerating cleaning solution according to Embodiment 1 of the present invention. Here, a quartz glass cleaning process in a semiconductor manufacturing process will be described as an example.

The hydrofluoric acid waste liquid discharged as primary cleaning water from the quartz glass cleaning step is a high concentration hydrofluoric acid waste liquid containing no impurities. Hereinafter, the high-concentration hydrofluoric acid waste liquid refers to a hydrofluoric acid waste liquid having a fluorine ion concentration of 3% or more.

First, the high-concentration hydrofluoric acid waste liquid containing no impurity is subjected to a simple water quality inspection step (step S1-1).
Here, the high-concentration hydrofluoric acid waste liquid is inspected for the content of harmful substances for each lot using a dropper-type simple water quality tester mixed with a detecting agent. However, since the hydrofluoric acid waste liquid discharged from the quartz glass cleaning step does not contain impurities as described above, harmful substances are not usually detected, and the subsequent step of adding nitric acid waste liquid (step S1-
It is carried into 2).

Next, a nitric acid waste liquid adding step (step S1)
In -2), 10 l of nitric acid is added to 1 l of the high-concentration hydrofluoric acid waste liquid.
By adding at a rate of ~ 200 ml, a regenerated cleaning solution whose pH value has been adjusted to an acidity range of 1.2 to 5.0 is obtained. Here, a nitric acid waste liquid discharged in a mesa etching step of a silicon wafer in a semiconductor manufacturing process is used as nitric acid, and the amount of the nitric acid waste liquid is an amount corresponding to 10 to 200 ml in terms of a nitric acid concentration of 100%.

As described above, the reason why the fluorine ion concentration is set to 3% or more is that if the concentration is less than 3%, it takes time to wash and remove the oxide film from the surface of the stainless steel pipe, and it is not possible to quickly remove the oxide film. is there.

The relationship between the amount of nitric acid added and the pH of the hydrofluoric acid waste liquid was set as described above, as is apparent from the data of FIG. 6, as shown in the data of FIG. Is linearly changed as compared to the hydrochloric acid waste liquid and the sulfuric acid waste liquid.
This is because the H adjustment can be easily performed, and the cleaning time and the cleaning ability can be freely controlled as required.

Further, by adding 30 ml of nitric acid to 1 liter of the high-concentration hydrofluoric acid waste liquid, the fluorine ion concentration becomes 3
%, It can be seen from the data in FIG. 5 that the pH value can be lowered to 3.0 or less. This allows
The cleaning process can be performed in a short time.

The dilute hydrofluoric acid produced from fluorite and sulfuric acid in the conventional example is a dilute hydrofluoric acid diluted with pure water, so that the pH value increases, the acidity decreases, and the cleaning ability decreases. Although it cannot be increased, the regenerating cleaning solution of the present invention
Since the pH value can be changed by adding nitric acid waste liquid to the hydrofluoric acid waste liquid, the acidity can be maintained at a constant fluorine ion concentration without adjusting to increase the acidity by increasing the fluoride ion concentration. You can take big. Further, according to the data of FIG. 5, it can be seen that the fluoride ion concentration tends to decrease in the hydrochloric acid waste liquid and the sulfuric acid waste liquid, so that it is not suitable for maintaining the fluorine ion concentration at 3% or more.

As can be seen from the following chemical reaction formula, it can be considered that the hydrochloric acid waste liquid and the sulfuric acid waste liquid generate hydrogen fluoride ions in addition to the fluorine ions, so that the fluorine ions are reduced. Because it seems.

<Reaction between nitric acid waste liquid and hydrofluoric acid waste liquid> HNO ₃ + HF → H ₂ NO ₃ ⁺ + F ⁻ HF → H ⁺ + F ⁻ <Reaction between hydrochloric acid waste liquid and hydrofluoric acid waste liquid> HCl + HF → H ₂ Cl ⁺ + F ^{− HF → H + + F - 2HF} + H + → H + + HF 2 - < reaction between sulfuric acid waste and hydrofluoric acid waste _{liquid> H 2 SO 4 + HF →} H 3 SO 4 + + F - HF → H + + F - 2HF + H + → H + + HF ₂ ^- Thus, even when the nitric acid waste liquid is added to the hydrofluoric acid waste liquid, a nitric acid-added hydrofluoric acid waste liquid having a stable fluorine ion concentration, that is, a stainless steel pipe cleaning liquid can be obtained without substantially lowering the fluorine ion concentration.

As described above, since it is only necessary to reuse the hydrofluoric acid waste liquid that would otherwise be disposed of, the fluorite or sulfuric acid required conventionally is not required, and the reaction furnace is used in the cleaning liquid generation process. There is no problem of large energy consumption,
The cleaning liquid can be manufactured at low cost. In addition, it is possible to prevent the problem of environmental degradation due to the generation of soot by using the reaction furnace.

(Embodiment 2) FIG. 2 is a flowchart showing a manufacturing process of a method for manufacturing a regenerating cleaning solution according to Embodiment 2 of the present invention. Here, a silicon wafer cleaning process in a semiconductor manufacturing process will be described as an example.

The hydrofluoric acid waste liquid discharged from the silicon wafer cleaning step is a high concentration hydrofluoric acid waste liquid containing impurities.

First, the high-concentration hydrofluoric acid waste liquid containing the above impurities is carried into a dilution step (step S2-1),
Here, pure water or a hydrofluoric acid waste liquid containing almost no impurities and having a fluorine ion concentration of less than 3% is added to dilute the fluorine ion concentration to be less than 3%. Hereinafter, a hydrofluoric acid waste liquid having a fluorine ion concentration of less than 3% is referred to as a low-concentration hydrofluoric acid waste liquid.

The reason why the high-concentration hydrofluoric acid waste liquid is diluted so that the fluorine ion concentration is less than 3% is that the impurities are removed with a filter in the next step (step S2-2).
If the concentration of the hydrofluoric acid waste liquid is high, the viscosity increases and the filtration speed decreases.

The above dilution step (step S2-1)
The low-concentration hydrofluoric acid waste liquid containing almost no impurities to be added in the above is one having an impurity-containing concentration equal to or lower than a wastewater standard value (0.1 mg / l or less) according to the Water Pollution Control Law.

Next, the diluted hydrofluoric acid waste liquid is passed through a filter in an impurity removing step (step S2-2) to remove impurities from the diluted hydrofluoric acid waste liquid. In addition, it is also possible to use a chelating agent that selectively adsorbs specific ions other than the filtering material to remove insoluble impurities such as organic substances and inorganic substances.

Thereafter, the diluted hydrofluoric acid waste liquid after passing through the above-mentioned filter medium is carried into the concentration step (step S2-3), and is passed through an ion exchange resin or a reverse osmosis membrane to obtain a high-concentration hydrofluoric acid solution.

Here, as the ion exchange resin, for example, a cation exchange resin or the like is used to adsorb soluble cations (mostly heavy metals are cations) into the resin, and fluorine ions are not adsorbed because they are anions. Concentration is possible by passing through the resin as it is and collecting only fluorine ions.
On the other hand, reverse osmosis membranes can be concentrated by applying a pressure higher than the osmotic pressure to the membrane and allowing only the water to permeate the membrane. Suitable for concentration. Therefore, high-concentration hydrofluoric acid waste liquid with a high impurity content is concentrated using a reverse osmosis membrane,
It is preferable to concentrate the low-concentration hydrofluoric acid waste liquid having a small impurity content with an ion exchange resin, but the present invention is not limited to this. In general, a reverse osmosis membrane made of an acetylcellulose-based or aromatic polyamide-based material has an advantage that it is less expensive than an ion exchange resin made of a methacrylic acid-based or acrylic-based material.

Thereafter, the concentrated high-concentration hydrofluoric acid waste liquid is carried into a simple water quality inspection step (step S2-4), where it is concentrated using a dropper-type simple water quality inspection device mixed with a detecting agent. Inspection of harmful substances is conducted for each lot of the high-concentration hydrofluoric acid waste liquid. However, since the impurities are not contained after being removed in the impurity removing step (step S2-2), harmful substances are not usually detected, and are carried into the next step, the nitric acid waste liquid adding step (step S2-5). You.

Next, a nitric acid waste liquid adding step (step S2)
-5), 10 l of nitric acid is added to 1 l of the high concentration hydrofluoric acid waste liquid
By adding at a rate of ~ 200 ml, a regenerated cleaning solution whose pH value has been adjusted to an acidity range of 1.2 to 5.0 is obtained. At this time, the use of a nitric acid waste liquid as nitric acid is the same as in the first embodiment.

Therefore, in the second embodiment, the same functions and effects as in the first embodiment can be obtained.

(Embodiment 3) FIG. 3 is a flowchart showing a manufacturing process of a method for manufacturing a regenerating cleaning solution according to Embodiment 3 of the present invention. Here, a quartz glass cleaning process in a semiconductor manufacturing process will be described as an example.

2 discharged from the above quartz glass cleaning step
The hydrofluoric acid waste liquid after the next washing water is a low-concentration hydrofluoric acid waste liquid containing no impurities.

First, the low-concentration hydrofluoric acid waste liquid is carried into a concentration step (step S3-1), and is passed through an ion exchange resin or a reverse osmosis membrane to obtain a high-concentration hydrofluoric acid waste liquid.

Next, the concentrated high-concentration hydrofluoric acid waste liquid is carried into a simple water quality inspection step (step S3-2).
The concentrated high-concentration hydrofluoric acid waste liquid is inspected for the content of harmful substances for each lot using a dropper-type simple water-quality tester in which a detecting agent is mixed. However, since the hydrofluoric acid waste liquid discharged from the quartz glass washing step does not contain any impurities as described above, harmful substances are not usually detected, and the nitric acid waste liquid adding step (step S3-3) is performed next. It is carried in.

Thereafter, a nitric acid waste liquid adding step (step S3)
In -3), 1 l of nitric acid is added to 1 l of the high-concentration hydrofluoric acid waste liquid.
By adding at a rate of 0 to 200 ml, a regenerating cleaning solution whose pH value is adjusted to an acidity range of 1.2 to 5.0 is obtained. At this time, the use of a nitric acid waste liquid as nitric acid is the same as in the first embodiment.

Therefore, the third embodiment can provide the same operation and effect as the first embodiment.

(Embodiment 4) FIG. 4 is a flowchart showing a manufacturing process of a method for manufacturing a regenerated cleaning solution according to Embodiment 4 of the present invention. Here, a cleaning process after an oxide film etching process of a silicon wafer in a semiconductor manufacturing process will be described as an example.

The hydrofluoric acid waste liquid discharged from the washing step is a low-concentration hydrofluoric acid waste liquid containing impurities.

First, the low-concentration hydrofluoric acid waste liquid is passed through a filter in an impurity removing step (step S4-1) to remove impurities from the low-concentration hydrofluoric acid waste liquid. It is to be noted that the removal of insoluble impurities such as organic substances and inorganic substances by using a chelating agent that selectively adsorbs specific ions other than the filter material can be adopted as in the second embodiment. .

Next, it is carried into a concentration step (step S4-2) and passed through an ion exchange resin or a reverse osmosis membrane to obtain a high-concentration hydrofluoric acid solution. Which one to use may be appropriately selected in consideration of work efficiency and the like.

Thereafter, the concentrated high-concentration hydrofluoric acid waste liquid is carried into a simple water quality inspection step (step S4-3), where
The concentrated high-concentration hydrofluoric acid waste liquid is inspected for the content of harmful substances for each lot using a dropper-type simple water-quality tester in which a detecting agent is mixed. However, since no impurities are removed and contained in the impurity removing step (step S4-1), harmful substances are not usually detected, and are carried into the next step of adding nitric acid waste liquid (step S4-4). You.

Thereafter, a nitric acid waste liquid adding step (step S)
In 4-4), 1 l of nitric acid is added to 1 l of the high-concentration hydrofluoric acid waste liquid.
By adding at a rate of 0 to 200 ml, a regenerating cleaning solution whose pH value is adjusted to an acidity range of 1.2 to 5.0 is obtained. At this time, the use of a nitric acid waste liquid as nitric acid is the same as in the first embodiment.

Therefore, the fourth embodiment can provide the same function and effect as the first embodiment.

[0066]

As described above, according to the first aspect of the present invention, the pH value is increased by adding 10 to 200 ml of nitric acid to 1 liter of hydrofluoric acid waste liquid having a fluorine ion concentration of 3% or more. To obtain a regenerating cleaning solution adjusted to 1.2 to 5.0. At this time, if impurities are contained,
It is desirable to go through an impurity removing step (Claim 2) and further a dilution step (Claim 3). On the other hand, in the case of a hydrofluoric acid waste liquid having a fluorine ion concentration of less than 3%, after concentrating the fluorine ion concentration to 3% or more as in claim 4, 10 to 200 ml of nitric acid is added to 1 l of the concentrated hydrofluoric acid waste liquid. By adding at a ratio, a regenerating cleaning solution whose pH value is adjusted to 1.2 to 5.0 is obtained. At this time, if an impurity is contained, an impurity removing step (claim 5) is performed.
Therefore, the cleaning liquid can be manufactured at low cost without using fluorite, sulfuric acid, and a reaction furnace without causing environmental degradation, and the pH can be easily adjusted according to the material of the metal product.
The washing time and the washing ability can be freely controlled by the adjustment.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a manufacturing process of a method for manufacturing a regenerated cleaning liquid according to Embodiment 1 of the present invention.

FIG. 2 is a flowchart showing a manufacturing process of a method for manufacturing a regenerating cleaning solution according to Embodiment 2 of the present invention.

FIG. 3 is a flowchart showing a manufacturing process of a method for manufacturing a reclaimed cleaning liquid according to Embodiment 3 of the present invention.

FIG. 4 is a flowchart showing a manufacturing process of a method for manufacturing a regenerating cleaning liquid according to Embodiment 4 of the present invention.

FIG. 5 is data showing the relationship between pH and fluorine ion concentration when nitric acid, hydrochloric acid, and sulfuric acid are added to hydrofluoric acid waste liquid.

FIG. 6 is a graph showing the relationship between the amount of nitric acid, hydrochloric acid, and sulfuric acid added to hydrofluoric acid waste liquid and pH.

FIG. 7 is a flowchart illustrating a manufacturing process of a conventional method of manufacturing a cleaning liquid.

[Description of Signs] S1-1 Simple water quality inspection step S1-2 Nitrate waste liquid addition step S2-1 Dilution step S2-2 Impurity removal step S2-3 Concentration step S2-4 Simple water quality inspection step S2-5 Nitrate waste liquid addition step S3 -1 Concentration step S3-2 Simple water quality inspection step S3-3 Nitrate waste liquid addition step S4-1 Impurity removal step S4-2 Concentration step S4-3 Simple water quality inspection step S4-4 Nitrate waste liquid addition step

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C23G 1/08 B08B 9/02 Z (72) Inventor Yoshifumi Kagawa 1-23-3 Makamicho, Takatsuki-shi, Osaka No.Shibatanai F-term (reference) 3B116 AA46 BB02 CD21 3B201 AA12 BB96 CA05 4H003 BA12 CA13 DA09 DA14 EA03 EA05 ED02 FA21 FA28 4K053 PA03 PA18 QA01 RA05 RA16 RA17 SA04 SA06

Claims (5)

[Claims] 1. A regenerated cleaning solution whose pH value is adjusted to 1.2 to 5.0 by adding 10 to 200 ml of nitric acid to 1 liter of hydrofluoric acid waste solution having a fluorine ion concentration of 3% or more. A method for producing a cleaning solution for regenerating and cleaning metal products, comprising: 2. The method according to claim 1, wherein impurities are removed from a hydrofluoric acid waste liquid having a fluorine ion concentration of 3% or more before adding nitric acid. For producing a regenerated cleaning solution. 3. The method for producing a reclaimed cleaning solution for metal products according to claim 2, wherein the hydrofluoric acid waste liquid having a fluorine ion concentration of 3% or more is removed before removing impurities from the hydrofluoric acid waste liquid having a fluorine ion concentration of 3% or more.
% Of the diluted hydrofluoric acid waste liquid after removing impurities from the diluted hydrofluoric acid waste liquid, and concentrating the diluted hydrofluoric acid waste liquid into a hydrofluoric acid waste liquid having a fluorine ion concentration of 3% or more. A method for producing a reclaimed cleaning solution. 4. A hydrofluoric acid waste liquid having a fluorine ion concentration of 3% or more is concentrated to a hydrofluoric acid waste liquid having a fluorine ion concentration of 3% or more.
A method for producing a reclaimed cleaning solution for metal products, wherein a reclaimed cleaning solution having a pH value adjusted to 1.2 to 5.0 is obtained by adding nitric acid at a ratio of 10 to 200 ml per 1 l. 5. The method for producing a reclaimed cleaning solution for metal products according to claim 4, wherein prior to concentrating the hydrofluoric acid waste liquid having a fluorine ion concentration of less than 3%, impurities are removed from the hydrofluoric acid waste liquid. For producing a reclaimed cleaning solution for metal products.